Electrical heating apparatus particularly for use with incubators



G. T." CHURCH 1,332,532

ELECTRICAL HEATING APPARATUS PARTICULARLY FOR USE WITH INCUBATORS Nqv. 17, 1931.

Filed March 27, 1929 2 Sheets-Sheet l Nov. 17, 1931. G. T. CHURCH 1,832,532

ELECTRICAL HEATING APPARATUS PARTICULARLY FOR USE WITH INCUBATORS Filed March 27. 1929 2 Sheets-Sheet 2 I Patented Nov; 17, 1931 5 NITED- srATEsrATENT OFFICE 5 ononsn-THoMAsonUnoH, or cHnn'rsEY, ENGLAND ELECTRICAL HEATING irrAnA'rUs"ram'rcunannzron UsE wrrn. m'ouBA'roRs "a lication filed Mai-ch27, 1929, serial No;

This invention relatesto electrical heating apparatus,particularlyintended for use with incubators or other chambers the temperature of which is required to be kept approximately constant. r v

Accordingto the inventlon a resistance serving as the heating'element is tapped at.

diflerent points which'are connected by leads to contact studs or the likeco-operating with a switch arm connected'jto one of the poles of the electric supplyjso that by moving the switch armmore orless of the resistance can be brought into the circuit to vary as required the temperature of the chamber in which'the resistance is'situated or with which it isasso ciated it being understood that the zero end of the resistance is connected to the other pole of the electric supply; The inventio'n'thus differs from those forms of electrical heating apparatus in which the control is effected by a rheostat arranged in series withthe -resistance forming the heating element.

When the heating apparatus is used incon junction with an: incubator orother chamber 15 only a few degrees.

the temperature of which is required-ktobe keptautomatically at a substantially constant level, I may provide means 'for-automfatically varying the amount of resistance in circuit in accordance with the temperature of the said chamber. The said means may be associated with a singles'witch armbut alternatively I' nay provide a second switch arm whichbears on a contact stud'appertaining to a resistance tapping below theone connected to the contact stud on which the first switch arm is for the time being resting and I provide a make and break device for auto-. matically connecting this second switch armto the pole to which the other switch armis connected, when the temperature falls below a certain level and for breaking theconnectlon when the temperature r ses above another level, the temperature being thus maintained.

between the said levels which may differby nThe said make and 350,420, and in Great B'ritain JuneB, 192 8.

break device may comprise a contactpiece and a spring contact member operated by a rod or other member under the influence of the usual capsule or other temperature controlled element, the contact piece being electrically connected 'to one'of the aforesaid switch arms and the contact member being electrically connected toitheother switch arm. The Tondswitch arm is electrically insulated from thefirst switch arm but "these arms are mechanically-connectedtogether'so that the second arm bears against a contact stud having a lower resistance value than that of thestud.

onwhich'the first arm bears. "The connected switch armsarefirst moved over the contact studs until the temperature'is slightly lower thanthat' which is required. The rod operhighest value of the resistance will provide too high a temperature and to prevent this I provide an additional no current or dummy contact stud on to which the first switch arm 'can be moved, the second switch arm then resting on the saidcontact stud appertaining to the highest value of the resistance; the temperature inside the chamber is thus maintained between that given by the highest value of the resistanceand that of the atmosphere of-the room in which the said chamber is situated. '7

In order that the said jinvention maybe more clearlyunderstood and readily carried into efiect, the same will now be described with reference to the accompanying drawings in which Figures 1 to 7 are views showing more or less diagrammatically several forms of electrical heating apparatus according to my invention.

In all the forms of electrical heating apparatus shown by the drawings, A is the tapped resistance which serves as the heating element and one end of which is connected to one of the poles (the negative for example) of a source of electric supply. The tapping points ofthe saidresistance are con nected by leads A, Ato contactstndsB, B-carried by an insulating plate B which may conveniently be arrangedina'box. Cooperating with these studs is a selecting switch arm C which is electrically connected bv a lead'C to,thcother pole of the source of electric supply.

The simplest form of the invention is shown in Figureilan'd. in'this form the switch :armi C is moved about a pivot'C (preferably by means of a-knob arranged outside the box containing the plate B) :to cause thesaiid zarm: to-rest on -any' one of the said studs, the selected stud bcing'that which'will give approximatelythe required temperature itbein unde stoodthat the-stud on'the left hand side-of Fierure 21 gives theahiszhest temperature andthe stud on' theright hand side the lowest temperature.

Figure 2 shows a forlirOflllP invention for use inrconi nnction with an, incubator or other ch mber the temperature of which is :requiredtobe kept ata substantially constant level and inthis iformasection. of the resistance A isconnectedby-leads A2. A to acon- .tactmointfDs and'to. a-spring make and break contact "member D whichis operated by a rod D under'the influence otthe usual capsule of the incubator. the arrangement bein 9, such that when'therodlD moves downwards on decrease of temperature the member D makes contact with the point D and thereby short-circuits the said isection of the resistance to increase :the tem erature; when the temperat re rises the rod D rises and the member D moves awav from the piece D. thereby bring ng the said section into circuit and-reducing the temperature.

[In Figure 3 there is provided a second switch arm C which bears on a contact stud P appertaining toa resistance tapping below the one connected't'o the stud on which the switch arm Cis resting at any time. This second switch arm is mechanicallyconnected to the switch arm C but is electr calli in ulated from itand tromthe pivot C which is in electrical connection withthe switch arm C. The second switch arm C is electrically connected to the aforesaid spring contact member .13 operated by :the rod D and the :arm- 1. wh ch connected bv thelea dC o the .positiveipolc, is also connected by a lead C to said switcharms C. C is mechanically connected to the others but the contact piece D. In this manner the rise of the rod D will bring into operation the portion of the resistance A between the arms C and C and the fall of this rod will shortcircuit the said portion. To prepare the apparatus for working the connected switch arms C, C are first moved over the studs B until the temperature of the chamber is slightly below that which is required and the rod D then adjusted until the member D bears on the piece D. Variations of temper-ature then vary the amount of resistance in circuit'as aforesaid andthe temperature of .thechamber is thus maintained within the required limits. The switch arms C, C are shownasbeingtwo contact studs apart but ifdeslred they may be only one apart or more than two; either or both of the said switch arms may be made ad ustahle so that their distance apart can be altered as required. T 11s ligureulso:shows at B 'the aforesaid no current m dummy contact'stud on which the switch arm .C can he moved, the switch arm C then resting on the stud appertaining tothe highest value of the resistance.

jF-igure 119811111131 to Flgurc 3 except for the provisioirof an extra heating resistance A uone end ofwhich is connected to the negative pole and the other to a knife contact A with which an extension C on the switch arm C engages when the 1 connected switch arms are moved to the maximum temperature position. The pnrpose-ofthis resistance A? is to providendditional heat for quickly heating a cold chamber to approximately the required temperature. This extra heating resistance may also be provided in the appara- :tu.s aceordmg to Flgures 1, 2. 6 and 7.

Figure 5 is also similar to Figure 3 except for the QDI'OVlSlOIl' of an extra heating resist- .anee A "which isalways in circuit when the apparatus-isinoperation and constitutes the .mainheating element. This extra resistance may also be provided in the apparatus ac- .cordingto Figures 1, 2, 6 and 7 Figure fishows a form of the invention similar to Figure 3 suitable for large heating apparatus and in this form there are two .make and break contact devices D, D the sprinn'contactmember of the additional device heingelectrically connected to an extra switch arm C situated between the aforc This switch arm C" isclec-trically insulated from them. The two springcontact members D may be operated. by separate capsule rods as shown-or by the same capsule rods if the said members are arranged in the same plane so that the said and can reston both of them.

Figure 7 shows another form suitable for a large heating apparatus in which, in order to reduce sparking at the make and break contact device D. D of Figure 3, a relay provided. In this construction there are E, E of which the blade E4 is electrically connected to one end of the coil of an electromagnet E and the blade E 1s electrlcally connected to one end of the coil of an electromagnet E the other ends of these coils being connected to the negative pole of the supply. Loosely pivoted on the pivot of the armature E is a lever E having projections E, E between which the armature E is free to move with a certain amount of lost motion. This lever has at one end an insulated bridgepiece E provided with points for dipping into mercury contained in cups E E and at the other end hasan adiustable weight E for balancing the lever. One of these cups is electrically connected to theswitch arm C and the other to the positive pole. The un and down movements of the capsule rod D e ergize and de-energize the electro-magnets E E, and the bridge piece E thusoperates to bring into the heating circuit the. section of the resistance A between the switch arms all) C. C or to short-circuit this section as required; This form of relay may be replaced by anvother form vsuitable for the purpose. The heating element A may be arranged in the flue pipe of an incubator, it may be clamped to the wa er tank of an-incubator or it may be arranged for fixing inside a hot air incubator or other chamber. aforesaid switch arms, contact studs and make and break contact member are arranged outside the incubator and are preferab y en closed in a box as aforesaid from which projects a handle or knob for operating the switch arms.

That I claim anddesire to secure by Let'- ters Patent of the United States is 1. Electrical heating apparatus comprising in combination a resistanceserving as the heating element, tappings at different points of said resistance, contact members. an adjustable switch member associated with said contact members, leads connecting said contact members to said tapping points, a lead connecting said switch member to one of the poles of the electric supply, another lead connecting one end of said resistance to the other pole of the electric supply, a second switch member bearing a contact member appertaining to a resistance tapping below the one connected to the contact member on which the other switch member for the time being resting, a temperature controlled clc-- ment and a make and break device operated by said element for automatically connecting In any case the said. .secondswitc'h' member toithe pole to which the other switch member is connected, whenthe temperature falls; below-a certain level and for breaking the connection when the temperature rises above another level.

Electrical heating apparatus comprisingin combination a resistance;servingas the heating element, tappingsatdlfierent points of said resistance,- contact lmembers.

an. adj nstable switch member associatedwitli said contact members,leads connectingsaid contact members to said tapping points, a leadconnecting said switch member to one of the poles of the electric,supply,'another lead connecting one end of saidiresistance to the other pole of the electric supply, a second switch member bearing on a contact member appertaining to a resistance tapping below the one connected to the contact member on which the other switch member is for the time being resting, a temperature controlled element, a makeand break device comprising a spring contact member operatedby said element and an associated contact piece, means for electrically connecting said spring contact member to one of the switch members and means for'electrically connecting said contact piece tothe other switch member.

3. Electrical heating apparatus comprising in combination a resistance serving as,

the heating element, tappings at different points of said resistance, contact members, a manually adjustable switch member associated with said contact members, leads connecting said contact members to said tapping points, a lead connecting said switch member to one of the poles of the electric supply, another lead connecting' one end of said resistance to the other pole of the electric supply, means for automatically varying the amount of resistance in circuit in accordance with the temperature of a chamber with which the heating element is associated, an extra heating'resistance, and means for bringing said extra resistance into operation when the switch member is in the minimum resistance position.

4. Electrical heating apparatus comprising in combination a resistance serving as the heating element, tappings at different points of said resistance, contact members, a manually adjustable switch member associated with said contact members, leads connecting said contact members to said tapping points, a lead connecting said switch member to one of the polesof the electric supply, another lead connecting one end of said resistance to the other pole of the electric supply, a temperature controlled element, a make andbreak device operated by said element for automatically varying the amount of resistance in circuit, an extra heat ing resistance, and means for bringing said extra resistance into operation when the switch member is in the minimum resistance position.

5. Electrical heatin apparatus comprising in combination wit the elements claimed in claim 1, an extra heating resistance and means for bringing said extra resistance into operation when the switch members are in the minimum resistance position.

6. Electrical heating apparatus comprising in combination with the elements claimed in claim 2, an extra heating resistance and means for bringing said extra resistance into operation when the switch members are in the minimum resistance position.

GEORGE THOMAS CHURCH. 

